High Rate And Selective Reactive Ion Etching Of Polysilicon

Abstract

With ever-decreasing feature size in devices along with increasing wafer diameter, single wafer plasma etchers have drawn much attention recently, because of uniform and reproducible etching as well as improved process control. High etch rate with good selectivity is necessary in order to economically compete with batch machines. In response to this requirement, a reactive ion etch process is developed that, by employing hydrogen bromide, provides both high polysilicon etch rate and high selectivity to gate oxide at the same time in an anisotropic etching of P-doped polysilicon. Furthermore, photoresist erosion rate is very low in the brominated plasma; there is virtually no linewidth loss in the processing even when the photoresist profile is substantially sloped. Silicon trench etching has also been achieved at high rate with HE3r-based plasma. The deep silicon trench with high aspect-ratio shows smooth etched surface, rounded bottom corner, and a slightly positive slope profile.